Holiday calendar: Mystery in the Gobi Desert

What are those strange white patterns in China's Gobi Desert? For weeks, experts have puzzled over the crazy lines that show up in satellite images.

Some of the theories have taken wild turns: Maybe they're messages directed at Earth-observing extraterrestrials, or part of a UFO development program, or the remains of ancient cities. But the leading theory is that these patterns serve a variety of purposes for the Chinese military, including calibrating satellite imaging systems and testing radar avoidance techniques. There have also been claims that these are "fractal antennas" to shield underground weapons facilities from ground-penetrating radar.

Whatever the precise purpose of these patterns might be, it's not all that unusual for people to draw huge lines in the sand: Consider Peru's famous Nazca Lines, which were etched more than 1,500 years ago to form patterns that look like geometric shapes, insects and birds. Some of those patterns can be seen in their full form only from the air. More recently, archaeologists have puzzled over wheel-like patterns in the Middle East.

What do you think about the Gobi puzzles? Feel free to add your comments below, and check out these past entries from the Advent calendar: